Low voltage voltage regulator, 3,4-6/3-5 volts 0,4 amps. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Surge Protectors

 Comments on the article

Despite the fact that microcircuits of low-voltage (3 ... 5 V) voltage stabilizers with a small voltage drop have now appeared, they are still not very common, especially among radio amateurs. But low-voltage stabilizers are now becoming of particular relevance. Almost all audio players are powered by a 3V supply, many modern radios also require this voltage, not to mention microprocessors. The devices brought to the attention of readers are an attempt to make such low-voltage stabilizers using affordable and inexpensive elements.

The circuitry of voltage stabilizers for powering devices with low-voltage power supply has its own peculiarities. For example, the simplest protection of stabilizers is most effective by limiting the maximum load current at a low output voltage.

The voltage drop across the regulating transistor of the stabilizer when the output is closed differs little from the working one and the transistor overheats slightly. It is very important for low-voltage stabilizers to reduce the minimum voltage between the input and output, since this increases not only the efficiency of the equipment, but also its reliability. For example, if a microcircuit is used in a three-volt stabilizer with a voltage drop across it also of three volts, then the rectifier supplying this device should supply voltage, taking into account ripples of about 9 V. If this voltage, due to a breakdown of the microcircuit, hits the load, it is very likely that it will come out out of service.

For a stabilizer, on the other hand, the voltage drop across which is less than 0,4 V, an input voltage of about 5 V is enough. A load designed for a three-volt supply is likely to withstand such an overvoltage. Until recently, there was a problem - to choose a source of exemplary voltage for a low-voltage stabilizer - a zener diode. Usually low-voltage zener diodes have very low parameters. The development of relatively simple low-voltage stabilizers, taking into account all of the above, allows the KR142EN19 microcircuit, an integral analogue of a low-voltage zener diode.

This chip is available in a plastic case with three pins. When the voltage at its control electrode relative to the anode is less than +2,5 V, the cathode current of the microcircuit does not exceed 1,2 mA, and it depends little on the voltage between the anode and cathode of the microcircuit. As soon as the voltage at the control electrode exceeds the threshold of +2,5 V, the cathode current of the microcircuit increases sharply until the voltage at the cathode drops to 2,5 V. The resistor connected to the cathode must limit this current to a value of no more than 100 mA.

The current of the control electrode is very small - a few microamperes, and this current should also be limited, since if it is increased too much, the voltage at the cathode of the microcircuit may increase.

Because the microcircuit is an analogue of a zener diode, then in the circuits it is switched on in the same way, in reverse polarity. The voltage at the cathode is always more positive than at the anode.

The circuit of a low-voltage voltage regulator on a KR142EN19 microcircuit with a regulating transistor in the positive conductor is shown in fig. 1.11. The voltage drop on this stabilizer does not exceed 0,4 V, and the stabilization coefficient is more than 600.

When the voltage on the output voltage regulator engine (resistor R7) rises to 2,5 V, the DA1 chip opens, which causes the transistor VT1 to open, the transistor VT2 to close, and then the regulating transistor VT3 to close.

With the voltage regulator R7, you can set the output voltage less than the 3 V indicated in the diagram up to about 2,6 V, however, during the switching on of the stabilizer, especially without load, a short-term increase in the output voltage to 3 V is possible.

This stabilizer can also be adjusted to a voltage of more than 5 V, but then it will overheat greatly when the load is shorted, since it is protected only by limiting the output current, which depends on the resistance of the resistor R2. The maximum operating current increases with a decrease in its rating.

If you need to significantly increase the output current of the stabilizer, you can try to reduce the values ​​of the resistors R1 and R2 by the same number of times and use more powerful transistors. In place of VT1, it is permissible to use a transistor of the KT626 series, and VT2 - KT630. We can replace the KT814A (VT3) transistor with any of the KT816, KT837 series with the maximum base current transfer coefficient.

The stabilizer should not use emitter followers to increase the output current. This increases the feedback loop time and can lead to excitation. If, nevertheless, self-excitation has arisen, it is necessary to increase the capacitance of capacitors C1 and C2, and also connect a capacitor with a capacity of several hundred picofarads between the cathode and the control electrode of the microcircuit.

A variant of a stabilizer with a regulating transistor in the negative conductor is shown in fig. 1.12. When the voltage at the control electrode rises to +2,5 V relative to the anode, the microcircuit opens and closes the transistors VT1 and VT2. The maximum operating current is set by selecting the resistor R2.

In the described devices, somewhat unusual output voltage dividers are used, in contrast to the traditional one, when a variable resistor is included in the upper arm according to the circuit. In this case, if the contact in the circuit of the variable resistor engine is broken, the voltage at the output of the stabilizers can only decrease, while when using a traditional divider, the output voltage reaches its maximum level, which can damage the load. In both stabilizers described above, in order to reduce the dependence of the maximum operating current on temperature, it is useful to provide thermal contact between the diodes VD1, VD2 and the heat sink of the regulating transistor.

If such stabilizers are used as adjustable, it is useful to include constants in series with variable resistors (to each extreme terminal). Their resistances should be selected so that the limits for adjusting the output voltage correspond to those indicated in the diagrams. In the absence of such resistors, the stabilizers can exit the stabilization mode in the extreme positions of the engines.

Author: Semyan A.P.

See other articles Section Surge Protectors.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Artificial leather for touch emulation 15.04.2024

In a modern technology world where distance is becoming increasingly commonplace, maintaining connection and a sense of closeness is important. Recent developments in artificial skin by German scientists from Saarland University represent a new era in virtual interactions. German researchers from Saarland University have developed ultra-thin films that can transmit the sensation of touch over a distance. This cutting-edge technology provides new opportunities for virtual communication, especially for those who find themselves far from their loved ones. The ultra-thin films developed by the researchers, just 50 micrometers thick, can be integrated into textiles and worn like a second skin. These films act as sensors that recognize tactile signals from mom or dad, and as actuators that transmit these movements to the baby. Parents' touch to the fabric activates sensors that react to pressure and deform the ultra-thin film. This ... >>

Petgugu Global cat litter 15.04.2024

Taking care of pets can often be a challenge, especially when it comes to keeping your home clean. A new interesting solution from the Petgugu Global startup has been presented, which will make life easier for cat owners and help them keep their home perfectly clean and tidy. Startup Petgugu Global has unveiled a unique cat toilet that can automatically flush feces, keeping your home clean and fresh. This innovative device is equipped with various smart sensors that monitor your pet's toilet activity and activate to automatically clean after use. The device connects to the sewer system and ensures efficient waste removal without the need for intervention from the owner. Additionally, the toilet has a large flushable storage capacity, making it ideal for multi-cat households. The Petgugu cat litter bowl is designed for use with water-soluble litters and offers a range of additional ... >>

The attractiveness of caring men 14.04.2024

The stereotype that women prefer "bad boys" has long been widespread. However, recent research conducted by British scientists from Monash University offers a new perspective on this issue. They looked at how women responded to men's emotional responsibility and willingness to help others. The study's findings could change our understanding of what makes men attractive to women. A study conducted by scientists from Monash University leads to new findings about men's attractiveness to women. In the experiment, women were shown photographs of men with brief stories about their behavior in various situations, including their reaction to an encounter with a homeless person. Some of the men ignored the homeless man, while others helped him, such as buying him food. A study found that men who showed empathy and kindness were more attractive to women compared to men who showed empathy and kindness. ... >>

Random news from the Archive Cardiograph in your pocket 16.02.2000 The German firm "Medisana" has started production of a pocket cardiograph. By pressing your thumbs on the contacts on the sides of a small box, after a few seconds you can see your electrocardiogram on the display. True, the device is by no means capable of replacing a real, large cardiograph. The result depends, for example, on the pressure applied to the contacts. The instructions say in bold type: "An abnormal ECG does not necessarily mean that you have serious heart disease. On the other hand, a normal ECG does not mean that you do not have serious, sometimes even dangerous, heart disease." That is, each owner of the device can interpret the results as he wishes. For nervous and suspicious people, as German doctors point out, such a cardiograph in your pocket can even be harmful.

Other interesting news:

▪ UAVOS drone with record run time

▪ LP3883 CMOS Voltage Regulator

▪ Lie detector for eggs

▪ Rosewill PB240-RGB Liquid Cooling System

▪ Artificial intelligence will help you choose a recipe

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Car. Article selection

▪ Armageddon article. Popular expression

▪ article How do we know what is at the center of the Earth? Detailed answer

▪ article by Aktey. Legends, cultivation, methods of application

▪ article One thermostat - several objects. Encyclopedia of radio electronics and electrical engineering

▪ article Do not rush to throw away an energy-saving lamp. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024